Slotted winged cylindrical antenna



Sept. 23, 1952 A. ALFORD SLOTTED WINGED CYLINDRICAL ANTENNA 7 Sheets-Sheet 1 Filed Aug. 51, 1946 INVENTOR. ANDREW ALFORD flmokx ATTORNEY A. ALFORD SLOTTED WINGED CYLINDRICAL ANTENNA Sept. 23, 1952 '7 Sheets-Sheet 2 Filed Aug. 31, 1946 Vertical Beam is Wide Vertical Section of Wave Front is Curved ELECTRIC FIELD ACK MOUNTING m G T w m O V 0 es .D wmq w. M 2 e \A r TII l 9. g 2 W r 0 e .l a G w m mrmw .l I l u .m D U N Is n nn m w U /\/\(\K\K\f\f\ u W .m ".SL 0 mmm. a er 2 sFm lemm V m UV 0 C O G 8W W F m V .m mm V ANDREW ALEORD "A A ATTORNEY Sept. 23, 19 52 ALFQRD 2,611,867

SLOTTED WINGED CYLINDRICAL ANTENNA Filed Aug. 51, 1946 7 Sheets-Sheet 5 FIG. 5.

INVENTOR. I800 ANDREW ALFORD W MA ATTORNEY Sept. 23, 1952 A. ALFORD 2,611,867

SLOTTED WINGED CYLINDRICAL ANTENNA Filed Aug. 51, 1946 7 Sheets-Sheet 4 FIG. 6o. O0

FIG. 6b.

INVENTOR. ANDREW ALFORD ATTORNEY Sept. 23, 1952 A. ALFORD 2,611,367

, SLOTTED WINGED CYLINDRICAL ANTENNA Filed Aug. 31, 1946 '7 Sheets-Shea}: 5

FIG. 2

FIG. 8.

INVENTOR. ANDREW ALFORD |80 BYA) a 'k ATTORNEY Sept. 23, 1952 A. ALFORD SLOTTED WINGED CYLINDRICAL ANTENNA '7 Sheets-Sheet 6 Filed Aug. 51, 1946 OONN INVENTOR. ANDREW ALFORD BY AWA ATTORNEY Sept. 23, 1952 ALFORD SLOTTED WINGED CYLINDRICAL ANTENNA '7 Sheets-Sheet 7 Filed Aug. 51, 1946 INVENTOR.

Ana re w 14/)? kg BY Au 01m 'ties and expense.

Patented Sept. 23, 1952 UNITED, STATES PATENT. OFFICE,

Andrew Alford, Cambridge, Mass. Application August 31, 1946, Serial No. 694,319

8 Claims. 7 (Cl. 250-33) This invention relates to new and useful improvements in antennas. Morespecifically, it relates to improvements in means for controlling the directivity of antennas for high frequency electromagnetic signals.

In making devices which will operate at ultra high'frequencies, many new problems arise but, at the same time, new approaches to the solutions both of old problems and new ones become possible.

One of the problems encountered in the development of television to be broadcast in the ultra high frequency region between 480 and 920 megacycles is that power-generating means capable of high power levels of modulated output are difficult to obtain. Besides the fact that technological and design difficulties are encountered in signal transmitters having high power levels, there are other difficulties which are outgrowths of the main problem. For example, equipment capable of putting out'large amounts of radio frequency power requires a correspondingly large wide band modulator, and this presents additional diflicul- Furthermore, such a high power radio frequency transmitter and wide band modulator consume large amounts of input power, because of relative inefficiency.

Accordingly, it is very desirable to make the "most effective use of amounts of power economically available in ultra high frequency operations, for example in television, "by securing a compensatingly high efficiency in some other part of the system (than the energy-generating source). Such another part of the system may be the power-radiating device, 1. e. the antenna. If the antenna is designed to emit energy in useful directions only, there will be an avoidance of wasted power, and so faras the service area is concerned, the power level will be increased by theantenna gain. From a practical standpoint, this is just as useful as increasing the output of the transmitter by an equal factor. Moreover, antennas, when once built, present a minimum problem of maintenance and renewal in contrast with the expensive high power tubes inthe transmitter.

Compact, economical, high gain antennas suitable for use at. ultra high frequencies are described in my copending applications Serial No. 640,690, filed January 12, 1946, Serial No. 641,692, filed January 17, 1946, and Serial No. 70,750, filed January 13, 1949, which contains all of the subject matter disclosed in my prior application Serial No. 644,519, filed January 31,1946, now abandoned. These applications disclose, slotted cylindrical antennas each of which emits radiant 2 energy concentrated along lines pointing su stantially towards the horizon if the long axis of the cylinder is vertical, and each of which has an unusually long aperture for a, device having a single feed point. Each antenna also features a loaded transmission line" along which RF energy moves with a phase velocity greater than the speed of light, wherebya simple feed system is adequate for a relatively large aperture and RF voltages along the aperture are in proper phase.

Another feature of those antennas is that they have suitable input impedances so that the feed in each case is accomplished by the direct connection of alow impedance feed line'to the antenna without the-use of critical transforming circuits.

Another feature is that the polarization of any one of these antennas, when it is mounted with its long axis in a vertical position, is horizontal. This polarization is a desired one because of general television broadcast practice.

Another feature of these antennas is that generally they are free from horizontal directivity.

Another feature of these antennas is that they have large operating band widths.

In certain applications it is desirable'to effect further economies in the use of radiating power by employing directivity in horizontal'planes as well as directivityin vertical planes. For example, if a transmitting station should be located alongside of a large body of water, such as a lake or ocean, or alongside a desert, itwould be asundesirable to waste radiant power over the water or desert (a non-service area) as to waste it by propagation directly upward. For this: reason, it is desirable to be able to control the" horizontal v directivity of any of these otherwise ideal radiators. In particular, because of the great advantages of the antennas described in my 'copending applications, it is especially desirable that means be devised whereby their horizontal directivity characteristics can be controlled without materially altering their other, presently useful, characteristics of efiicient vertical directivity, suitable input impedance, horizontal polarization, and broad operating band. i

It is an object of this invention to devise means adapted to control the horizontal directivity of slotted cylindrical antennas witho tv materially altering their'useful characteristic s.Q Other objects, features and advantages ofthis invention, will be apparent from the description which follows and from the drawings in which:v

Fig. 1 is an isometric view of one embodiment parallel to the long axis of portion I.

of a slotted cylindrical antenna in which a portion of the cylinder adjacent to the slot is broken away to show the feed line;

Fig. 2 is an isometric view of an antenna as in Fig. l, with the addition of structure comprising wing elements according to this invention;

Fig. 2a is a diagrammatic representation of an ordinary electromagnetic horn and of some of its characteristics;

Fig. 2b is a diagrammatic representation of an embodiment of this invention and of some of its features in a manner corresponding to the representation of Fig. 2a;

Fig. 2c is a diagrammatic representation as in Fig. 2a. with respect to another ordinary electromagnetic horn;

Fig. 3 is an isometric view of a mast mounting of another embodiment of a slotted cylindrical antenna employing wing elements according to this invention:

Fig. 4 is a diagrammatic representation of a transverse cross section of the antenna and mast of Fig. 3. It does not include any representation of the ladder.

Fig. 4a is a diagrammatic representation of a transverse cross section of an embodiment of this invention having structure similar to that of the embodiment of Fig. 3, but different therefrom in that structural simplifications have been effected whereby the mast and the wing elements are formed as a unitary structure;

Fig. 5 is a polar diagram showing the horizontal directivity of an antenna as in Fig. 1;

Figs. 6, 6a, 6b, 6c and 6d are similar polar diagrams showing the horizontal directivity of the antenna used in obtaining the plot of Fig. 5 after it was modified by the addition of various embodiments of wing elements. The diagrams offer a convenient means for comparing effects on hori- ,zontal directivity of the use of difierent amounts of angular spread between the wing elements and of other variations in the manner in which the wing elements are applied.

Fig. 7 is a polar diagram showing the horizontal directivity of an antenna as in Fig. 4

Fig. 8 is a polar diagram showing the horizontal directivity of another embodiment of the present invention;

Fig. 9 is a diagrammatic representation of another embodiment of a slotted cylindrical antenna which may be used with wing elements according to this invention;

Fig. 10 is a diagrammatic representation of another embodiment of a slotted cylindrical antenna which also may be used with wing elements according to this invention;

Fig. 11 is a diagrammatic representation of an array composed of slotted cylindrical antennas either according to Fig. 9 or 10 and including wing elements according to this invention;

Fig. 12 is a diagrammatic representation of the manner in which structure may be added to an array as in Fig. 11 to protect it from the elements; and

Figure 13 shows in perspective a single unit antenna of the present invention.

The slotted cylindrical antenna of Fig. 1 has a cylindrical body portion I with a longitudinal opening, slot 2, in one side which extends along substantially its full length and is substantially A coaxial feed line having an outer conductor 3 and an inner conductor 4 extends into the interior of portion I with the outer conductor 3 lying adjacent to its inner wall and near to one edge of '4 slot 2. An electrical connection (not shown) is made between outer conductor 3 and the conductive structure of portion I at a point preferably near to one edge of slot 2-the edge which is on the right of slot 2 as the slot is shown in the drawing. Inner conductor 4 is electrically connected to the other edge of the slot at a point substantially midway between its ends, and the connection may be made through a triangularly shaped (dog ear) piece of conductive sheet material -5 whose intended electrical function is to reduce reflections which might occur at the point of connection. Slot 2 does not extend to the ends of portion I. Therefore, substantially zero impedance terminations occur at both ends of the slot. This particular embodiment of a slotted cylindrical antenna is center fed. It employs a cylinder of circular cross section; it has fixed (non-adjustable, i. e. non-sliding) short circuits at both ends of the slot; it is made of solid metallic material in the structure of its body portion; and it is fed by a coaxial line. However. this particularsingle embodiment is shown herein only to indicate, as shown in Fig. 2 and as described below, the manner in which modifyin structure employed according to this invention is added to a typical slotted cylindrical antenna.

The improvement in slotted cylindrical antennas according to this invention may .be applied to the structure of any slotted cylindrical antenna and, in particular, to any of the various antennas described in the above-mentioned copending applications. Therefore, the scope of this invention includes many embodiments which may be derived by various combinations of antenna structures described in those applications and appropriate forms of the modifying wing structures described herein.

In many embodiments of slotted antennas, the cylindrical body portions are formed with cross sections which are not circular but instead may be rectangular, oval, square, triangular, or irregularly shaped. In certain embodiments, the physical structure of the body portion is not a mechanically continuous structure of conductive material, 1. e. is not identical to a smooth piece of sheet metal bent into a slotted cylindrical tube, but may be of wire netting, of a stack of hooplike structures having a common axis, each hoop being open at one side and having the ends of its opening abutting on and fastened to parallel wires which electrically are similar to the edges of slot 2, or of plastic material with conductive material afi'ixed to or embedded in it. The physical structure, in fact, can be varied freely, without markedly changing the electrically efiective composition of the antenna.

In many embodiments certain short-circuiting elements are movable along the slot for adjustment purposes. Some employ a single short circuit which may be near one of the ends. Some are not short-circuited at either end, and some use a plurality of short circuits and of feed points. The feed may be effected through parallel transmission lines or through coaxial lines. It may be applied at the center of the slot or at other points, as, for example, at one of the ends. The slot and/or the ends of the Cylinder may be mechanically sealed, as with a dielectric plastic. The antenna may be mounted on a mast or may comprise its ownsupporting structure, as, for example,'when it is set up on one of its ends on a ground plane," such as a metal roof. Conductive structure may be inserted within the body portion to control the electrically effective crossfrom the edges.

the cylinder.

Kaela- ,867

sectional area by what mayi'be described as shortcircuiting someof the space therein. In-fact,.in

the feed point will be of the' same cross-sectional area as the half through which the feed lineextends. I a

In some embodiments the cross-sectional area of the cylinder and/or the slot-length are critical in determining directivity and gain, and-theislot width and the thicknesses of. the opposing edges of the slot must also be substantiallyinaccordance with predeterminedspecifications. Fig. 2 substantially comprises the structure Fig. 1 with the, addition of structure comprising wings I and 8. As is indicated in the drawing, wings I and 8 may be parts ofasingle sheet of conductive material, such as-metal. A slot of about the same size as slot ZOfFig. 1 is cutin this sheet and the sheet is electricallyconnected to portion I, with both edges and both ends of the two slots substantially coincident. The connection may be made by any convenient means, such as soldering, welding, bolting or riveting. The wings, in the embodiment shown in Fig. 2, have .an angle of divergence between their front surfaces, i. e. an angle ofdivergenc'e measured between their surfaces on the forward side of the slot, that is greater than 180; However, the wings may be initially installed or later bent so asto have different desired ang'lesfof divergence. The angle selected will have a specific effect on the horizontal directivity of the antenna If desired, each wing may be a separate sheet of metal. The wings, or the unitary structure comprising them, may be of some physical structure other than solid sheet metal but, nevertheless, electrically equivalent thereto. As explained below, in some embodiments the wings-may be.

constructed so that even electricallytheyrepresent conductive areas which are somewhat less than continuous and uninterrupted. The wings may be attached precisely on the edges of the slot or they may be attached on'elongated areas of the outer surface of the-cylinderwhich are substantially parallel-to the-edges ofthe slot but are located at predetermined distances back When the antennaof Fig! 1 is'energized, the

potential thus existing.betweenouter conductor 3 and-inner'conductor l is applied across slot 2. By making portion 1 of such sizeithat its inside cross-sectional area is of. the order. of v.014. square wave length, it is possible to producea substantially co-phasaldifierence of-potential over the "entire length of slot 2 when theslot is approximately two waveY-lengths I long. "The currents produced by, the' difierences';of-potential existing across the slot flow circumierentially around The field "which is radiatedby these circumferential currents -is similar "to that "which wouldbe radiated by astack consisting of a large numberof small coaxial loops. The ra- 'diant field-is horizontally polarized when the long axis of the cylinder is vertical. The maximum field is radiated in theplane perpendicular to the axis of the cylinder and passing through its center. The'minimum fieldis radiated. in the direction of the long axisof the cylinder; 'When the length of the slot is approximately two wave lengths, the inside cross: sectional area-is. approximately .014 square wave--ilength,-*and the slot "width is of the order of 5 .01 wave :lengthy the radlationpatte'rn in aplane-passing. through-the g axis of I the cylinder consists' of t'wo opp osing narrow major lobes with maxima at right -angles to the cylinder axis. When several such antennas are arranged in a vertical-'arraywith the individual antennas mounted one above another; still 'greaterconcentration" of radiant powerisa-obtainedin a horizontal plane, that isyinthe' directions ofthe service areas. The main advantage of the slotted cylindrical antenna is thata great concentration of radiant energy maybe obtaine'd with only few individual elements and; therefore, also with few branch feeders; fittings'an'd otheritems of feeder hardware.

- antenna-of the elements herein designated as wings. v The difference of potential across the slot produces a flow of currents in the wings. The

I predominant direction of'thecurrenti's at right angles to the long axis of theslot. The currents, which in a slotted cylindricalantenna without wings are circumferential';'are, at least: in part, diverted into the added wings. This :change in the path of the currents results in changes"- in radiation patterns in planes at right angles t'o the cylinder axis. By controlling the size of the wings, their shape (for example,"by making the wings not rectangular but With 'curvednor serrated edges), and-the angle between -them,- it is possible to controlthe' radiation' patterns in planes perpendicular to the cylinder axis.

The fact which makes this methodof controlling the pattern particularly useful is that' the a addition of wings to a slottedcylinder antenna does not destroy its main advantage of concentrating radiant energy in the plane'at right angles to the axis of the cylinder and passing through the centerof the cylinder. "Contrary to what might be expected,'tests showzthat the addition of wings to a, slotted cylindrical antenna produces only small effect on the propagation velocity along the slot and that this velocity ofpropagation and, therefore. also the distribubution. Because of these phenomena, 'the :design of efiicient antennas with wings'is' made relatively very simple. The 'dimensionsmflthe =s1otted: cylinder are chosenas if no Ewing'swwere to "be added. The wings of desired shapeare then added to thecylinder. Since: good concentration of radiant power is obtained withcslotted [cylinders having cross-sectional!Jareas-v of athie order of .014 square wavelength; the --:same' di-' mensions hold good for cylinders :with wings; Minoradjustments of slot length.) are sometimes necessary with some of 'thewing. arrangements.

but. these adjustments may. easily be made... for

example, by providing the slot, with .movable short-circuiting bars. As the angle between the wings is madesmaller, for ;example;under -,--theloading effect. of .the wingsbecomes -more' pronounced. This loading efiect-ofethe =wings may be contro11edi.;by. changingatheocapacity per unitxllength. between. thee-.edg.es,iof';.ihe

slot. By increasing :this capacity per unit i length, "for example by narrowing the slot, making the edges of the slot wider, or by usingv a dielectric in, the slot whose coeificient is greater than air or by a combination of the above means, the coupling. between the wings and the cylinder is decreased and, therefore. also the loading effect of the wings is decreased. The-effect of the .inicreased capacity on the propagation of waves inside the cylinder may be compensated for by decreasing the cross-sectional area of the cylfinder. Thus, even when the angle'between the wings is relatively small it is 'still possible to pro- 1 duce co-phasal excitation of a slot which is longer than one wave length at thecenter-frequency of the operating frequency "band.

In order'to explain another feature of the present invention, theslotted cylinder radiator with wings will be compared with.anordinary electro- :magnetichorn, shown in Fig. 2a. Such a horn consists of aflared horn portion ID, a length of waveguide H, and a stub wave guide feeder 12. It is general practice to make cross-sectional di- -mensions of the waveguide such that the long dimension '2) is .less than .one wave length but greater than a half wave length, and the small dimension-a is approximately one-half of dimension b. Dimension b is made less than one wave length in order to avoid the generation of the second mode of propagation which, if present, would distort the beam produced by theflare of the horn. It'is well known that by diverging the sides of the flare a narrower beam in the'vertical plane may be achieved, but thatvbecause of the divergence of waves in the flare, the vertical secition-of the wave front is curved and, therefore, for a given aperture size, the beam-is not asnarrow as it would be if the wavefront section were -a straight line, which would be the case if the :excitatiomof the waves were cophasal. In contrast with the ordinary-horn the slotted cylinder antenna of this invention ismade approximately .two wave lengths long, so that the apertureof :two wave lengths may be excited co-phasally. Therefore, a cylindrical and not spherical wave front is produced so that,-for a'givenvertical size, .a narrower 'beamin vertical planes is obtained. .Thisco-phasal excitation of the aperture and, -.th erefore, inarrower beam are made possible through the action of the cylinder havinga crosssectional areaof the order of .014 square wave length. .Acomparison of Figs. 2a and Zbclearly shows this distinction. Though the largest vertical dimension of thehornis aslar-geas that of -the slotted cylindrical-antenna (with wings), the vertical directivity of the horn is far less pro- .nounced.

Still another distinction between the slotted cylinder with wings and the electromagnetic horn visi that the wings maybe bent back, as in Fig. 2, makingan angle Lover 180 without affecting the "narrowness of the beam in vertical planes. When .the flare of an'electromagnetic'horn is bent back in thefsame mannena wide beam is obtainedin thevertical plane because there is no way for the wavestodiverge to a greater-effective .aper- :ture. The'original'waveguide aperture, which .ais less than one wavelength, .is, therefore, :the :effective :aperture, and. the "corresponding beam is wide.

' isobvious in Fig. 20, it is possible toiincrease ithe "directivity of a horn without increasing :the -sizeof-its-aperture. This mayrbe done byrincreasing thelength dimension (dimension D in i' mazo) l-lowever, aihornicomparable. in directivity to aslotted cylindrical antenna of equal :at'apoint2l which is approximately one-quarter wave length below the center of the cylinder. The distance Sfrom point 2! to the short-circuiting'plate 22 is made approximately one and onequarterwave lengths long. Short-circuiting bars 23, 24 are-connected to both sides of the slot at points which are-equidistantfrom point 21. Distances L from the short-circuiting bars to point 21 are adjusted for best-distribution of the-differences of potential along'the two edges of the slot. When the cross-sectional area of the cylinder less the cross-sectional area of the inner conductor'is of the order of .014 square wave length, good results are obtained by making each distance L approximately one Wave length long. In this arrangement, cylinder l5 performs a least three functions: Cylinder I5 acts as the-radiating element, as the outer conductor of the concentric feeder, and as a distributed inductive element providing the required loading for the balanced transmission line consisting of the edges of the slot.

This arrangement is particularly convenient when the operating frequency is very high because then .the diameter of cylinder! 5 is too small for the installation of -a concentric feeder in themanner showninthe embodiment of Fig. 1.

Fig.v 10 shows what is,.in effect, anarray of two cylinders .ofthe. kind shown in Fig. 9. This structure-consists ofa single slottedcylinderBU which is energized by concentric feeder 3|. .The inner conductor of feeder 3| is continued along the axis of cylinder 3! to short-circuiting .end ,plate 32. Two branch feeders 33, are used to connect "the inner conductor 35 to'the same edge of the slot atpoints 36,31. The branch feeder 33 is connected at distance S equal to approximately one andone-quarter wave lengths from the end plate --32. The short-circuiting bars 38 and 40 and 39 and 40, respectively, areplacediat equal distances L, 'approximately'equal to one wave length-from points'36 and 31.

Since the distance along inner conductor 35 between the branch feeders 33, .34 is substantially two wave lengths, thesame edges of the :slotare energized in phase. ICo-rphasal excitation is, therefore, obtained throughout the entire length of a slot'four wave lengths long. A similar system may .be .used to excite a slot six or eight wavelengths in length.

Slotted .cylindricalradiators of the types shown in Figs. 9 and IOmaybe equipped with wings in -.the same Way asradiators of the type 'shown'in Fig.1.

'A plurality of slotted cylindrical radiators, as lniFlg. Qor-Fig. 10, provided with pairs of wings which make. angles of 'thegorder-of 140, maybe v.combined'togethentoform a very directional ,ar-

:ray, as shown in 'Fig. :11. and-41 :arenelements like the antennas of Fig. 9 :orFig." 10 equipped;with'wings. .All of theele- :ments areconnected toa main feeder 48 at points .separatedby one wave length, 1 Such anarray will In this figure 45, '46

provide. :very; high power gain" per cubic foot of array L I Fig; 12 shows convenient structure for protect ing an'array asin Fig; 11 from the elements. Dielectric cover -box=i50,-which; may conveniently be made of fibre. glass, can be placed over thearray with its open. endabutting against thehback mounting plate.- Moreover, wires may beembedded in box 50 through whichcurrents .may be passed -inorder to-heatthe box andmelt ac cumulations of ice or sleet. Since the, electric field at points in front of. such an array is at right I angles to the direction of the slots, wires such. as 5l.r'n"ay pass infront of the array and have substantiallyv no effect. These wires may be embeddedin-the thin sheet offibre glass; composing box- 5!) and used asheating elements for removing sleet from thefibre- .glass while the fibreglass sheet itself is used toexclude water from the slots.

A fewof a large variety of horizontalpatterns whichQmay. be achieved. by the -use of slotted cylinder radiators with wings are shown in Figs. 6, 6a, fibfll'and' 8; Figs. 6, 6a, 6b and B'show the major trends which may be expected with straight wings with or without a back plate behind the antenna.

Fig. 6c shows ".theefiect of bending theedges of straight wings. When the dimension S shown in' Fig. 6c is ofrthe order. of one to.,several;tenths of the wave length, the potential along edge 55 of wing 56 is different from the potential'of the portion of wing'56 opposite edge 55, behindfthewing, and the space between edge .55 andgthat, portion forms a wideradiating slot; A similar slot-is formed byedgee5'l and wing-58.1 The ef-v fect of these secondary slots is. :to send vback radiation in a phase opposite to that-ofthe minor lobe:in Fig. ea, thus-eliminating this minor lobe..

By 'making the, solid-wings into a comblike. structure, consisting only of a few rods, theeffect of the wings isrdecreasedand a pattern of the type shown in Fig. 6d.may= be obtained. 1 Still another type of pattern may'b had byv bending the wingsaround a tubular mast. This is shown in Fig. '7 This pattern was v.obtained with a twenty-inch mast and with the-radiator operatingat 450 me. The effect of;such'objects as'metalladders .or feeders behind large wings is. minonunless metal, objects behind: the wing, have dimensions greater than thewingaitself.

This is true even when the: Wings are bent around a.mast, as in Fig.3.- i v-Fig. 4a shows still anotheritype of-wing which isatub'e of circular .cross .section;- Itiiwill be seen-from theabove description of the slotted cylinderqwith wings that the cylinder performs the function of a feeder' for 'theiwings and may, therefore, be called a feeder 'cylirider'. The-wings are the radiators; I'nEsome-cases only asmall portion of thetotal current is diverted into the wings, for example in the'case of $116 radiator .of Fig. 6d. Then, the outer surface of the feeder cylinder itself also performsthe: function of the Wings. *1 This is an example of a'divided wing. x The-shape of thefeeder cylinder need .not be circular. Whatever-the shape of :the11cylinder cross -section,--the cross-sectional area of the cylinder-should be. orthe order of betweencfiland .02-square .wave length andpreferably of the order1of .0l4square wave, length.

:In. some cases when the slot is loaded capacity of I thick wedges; of theasloti .oraby other 10 Alsozwith some wing arrangements it maybe necessary to use a cross-sectional area greater than .02 square wave length. When there is some doubt as to what value of thecross-"sectional area should be used, it is best to measure the distribu tion of potential differences along the slot. The correct value of the cross-sectional areashould' result in-the potential difierencesalong thejslot being distributed in the following w ayz.v ,j (1) The maximum of potential sh uld ccur'atl points intermediatebetween the feed point and the 'short-circuiting points (or .bars) along the,

(2) The potential should decrease from the maxima toward the feed point, withoutj there being distinct minima between the maximajand the-feed points; i. Q

,;(3) Thecorrect cross-sectional area should re suit-in a potential difierence distribution of this .kind when the distance between the .short-cir -lj cuiting bars is of the. order' of two wave lengths; assuming that both ends. of the slot are short circuited. ...In one embodiment of this invention, thewings. are added to a feeder cylinder which is made not of e a sheet of metalbut of anumber o f coaxial loops, as described-in the 'copendingapplication No. 70,752, filed January 13, 1949, which contains all of the subject 'matter'disclosed my prior application No. 644,519, filed'January 31 "1 524.6;

now abandoned This typefof structure isf're -fl erred to in the specification above and m ay'com prise asstateda stack of hoop-likestructures having a common axis each being open at one side and having the ends of its opening abuttiri'g'{ on-andfastened to parallel "wires which 'electri cally are similar to the. edges of slot 2 in Figure -1, Experimentshows that if the wing's'are ma'de of rods, twofrods per each loop. or two rods per every other loop, or two. rods per'every'third loop, the best dimensions of the feed xylinderf are not materially alteredf thatfis. they still; should be as described in said copendingapplica tion. Thetypes'of patterns'which be'obtained; with this arrangement are similar t thosef d {j scribed in connection with sheet 'metalcylinders The. effect. of the wings "is reduced when they are constructed of two rodsper every other loop" andthis effect is still furtherreduced when two rods arelused' for everythird loop, andsd man The velocityof propagation of potential alongthe slotmay befland us ually is greaterlthan are velocity of the waveinfree space; Theresult or this is that the wave length for the givenifre -f quency of operation is increased. "This isI-dueJ-ki the use of the pro'per relationsbetween the 11:6 quency and the inside .efiectivec'ross' sectional area of the slotted cylinder and to a minor degree by the means, theicros'sr'sectional area for; best results;

may :be. even less. than. .101 square. wave length.

I eut i q si 'e i. a s e19 theoharacter of the air gap of the' slot although" the usual slot as described aboveis satisfactory; The. wave length along the slot wherespecified asdifierentiated from that in free space is'called;

the virtual Wave length and is ss s 1 claims. I

cylinder with the outer' conductor connected tothecylinder adjacent'the slot or gap H on one side and" the inner conductor connected across the. gap-on the other side'as shown at 16, The cylinder has such dimensions that its cross sectionalfiarea should. be of the order between .01 and .02 square wavelength and preferably ofthe" orderof .014 squarewave length of a frequency radiated by the slotted. cylindrical antenna as set forth previously in; the specification.

.The width of the wing; as indicated in all of the" figures should be largerthan the'cylindrical diameter and these Wings should open outwards from the slot in non-parallel directions one with the other.

What I claim is: v

14 An. antenna including a slotted cylinder formed by an elongated aperture in one of' its sides along its length, means for feeding radio frequency energy to the slotted cylinder with onposite potentials across the slot, and radiating wing elements attached to the exterior of the cylinder near to the aperture, said wing elements having length and widthdimensions for producing. ina substantially predetermined manner the directivity of radiations of. energy from the aperture concentrated in: a region in a plane perpen dicular to the slot, the inside cross-sectional area of said slotted cylinder being substantially between. .01 and..02.'square wave length, the wave length. corresponding to-the. center frequency of the operatingf-requency band, saidwings having widthsnot less. than the diameter of said cylinder and extending from the direction of the cylinder in diverging, directions.

2. An antenna. comprising a cylinder-having a slotopen at one end, ashort circuit near the other end of. the slot, and, means feeding the cylinder on opposite sidesof the slot for exciting the cylinderto produceequal butopposite potentials along theedges' of the slot, said cylinder having an internal cross sectional. area and an air gap capacity-computed to produce a voltage distribution whose maximum is: at a greater distance from the short circuitthan two-fifths of the space wave length, and radiating wing elements attached to the-cylinder near the edges ofitheslot; said wing elementshaving length and width dimensions for producing ina' substantially predetermined manner the directivity of the antenna in planes normal tov theaxis of the cylinder, said, wings having widths not less than the diameter of said cylinder and: extending from the direction of the cylinder in diverging directions.

3. An antenna.- comprising a cylinder of con ductingmaterial having a longitudinal slot, short circuit. elements across the. slot near the ends thereof, means for feeding the antenna at points acrossthe. slot to produce a potential difference betweenlthe. edges of the slot, said points being at. agreatendistance from the short" circuit elements than the virtual half wave length but less than a full virtual wave length of the standing" wavealong the slot whereby, the potential distribution along the slot has two minimum points, causing, the how of currents in the outside surface of the cylinder in proportion with the potential di'fi'er'ences and in one direction between the minima andthe short ends, and in the opposite direction between the minimum points, and energy-radiating electrically effective Wing elements electrically connected to the edges of the slot and having length and width dimensions for producingin a substantially predetermined manner the distribution in planes normal to the axis of the antenna ofen'ergy transmitted; therefrom,

said wings having widths not less than the diamlength corresponding to the center frequency of the operating frequency bandand a slot in the cylinder parallel with its. longitudinal axis, the slot having a short-circuited element near. one end, a transmission line projecting Within, the cylinder and having an inner and an outer conductor, the inner conductor-being. connected with one edge of theslotatthe openend' of the cylinder, the outer" conductor being connected to theother edge of the-slot, and energy-radiating electrically efiective wing elements: electrically connected tothe edges of: the slot; said wings having widths not less than the diameter: of. said-cylinderand extendingfrom the directionof the cylinder in diverging directions.

5. An antenna for radiating horizontally polar-- ized electromagnetic waves at ultra high frequencies, including a vertical cylinderv having an open end and having a longitudinal slotrunning along substantially its whole length, a conductive disc attached across one end of. the: cylinder; substantially perpendicular-to its: long, axis, an inner conductive element electrically'connected at substantially the center of the disc and extending therefrom along the axis of. the cylinder for its full length and protruding'beyond the open end of the cylinder, a tapered matching section shaped like the curved side of. a truncated cone, its large open end, being of the same diameter as the open end of thecylinder-and being electrically connected theretoso that the tapered section has its long axis coincident with the extension of the long axis of'the cylinder, a coaxial transmission line whose inner conductor consists of the extension of said inner conductive element and whose outer conductor has the same diameter as the tance between any two adjacent short-circuiting elements is substantially two space wave lengths, the wave length corresponding to the center frequency of the operating frequency band, a feed conductor means joining the, inner conductive element to one of the edgesv of the slot at each point which is substantially midway'between any two short-circuiting elements, and energy-radiating electrically effective wing elements electrically connected to the edges of the slot and adaptedto ailect in a substantially predetermined manner the distribution in planes normal to the zfilzisof the antenna of ener y transmitted there- 6. An array consisting of a back mounting plate supporting a plurality of antennas as in claim 5, with means for feeding the respective coaxial transmission lines of each of said antennas with radio frequency energy in the same phase.

7. An antenna including a cylinder with an elongated slot in one of its sides along its length, means for feeding radio frequency energy to the slotted cylinder, and radiating wing elements attached to the exterior of the cylinder near to the slot, said wing elements having length and width dimensions for producing in a substantially predetermined manner the directivity of radiations of energy from the aperture, the inside crosssectional area of said slotted cylinder being substantially .014 square wave length, the wave length corresponding to the center frequency of the operating frequency band, said wings having widths not less than the diameter of said cylinder and extending from the direction of the cylinder in diverging directions.

8. A combination of a slotted cylindrical radio frequency antenna, means for feeding the antenna effectively on both sides of the slot, energy radiating wing elements electrically connected to the cylinder and extending outward therefrom adjacent the outside of the slot all along the same on both sides thereof, said slot being substantially two wave lengths long with an efiective inner cross sectional area of the cylinder substantially between .01 and .02 square wave length where the wave length corresponds substantially to a frequency within the operating band, said wings having widths not less than the diameter of said cylinder and extending from the direction of the cylinder in diverging directions.

ANDREW ALFORD.

REFERENCES CITED The following references are of record in the file of this patent:

14 UNITED STATES PATENTS Number Name Date 2,206,923 Southworth July 9, 1940 2,210,415 Kellogg Aug. 6, 1940 2,234,293 Usselman Mar. 11, 1941 2,238,770 Blumlein Apr. 15, 1941 2,241,119 Dallenbach May 6, 1941 2,253,501 Barrow Aug. 26, 1941 2,292,496 Von Baeyer Aug. 11, 1942 2,297,202 Dallenbach et al. Sept. 29, 1942 2,400,867 Lindenblad May 21, 1946 2,402,622 Hansen ...1 June 25, 1946 2,405,242 Southworth Aug. 6, 1946 2,414,266 Lindenblad Jan. 14, 1947 2,415,094 Hansen et a1 Feb. 4, 1947 2,433,368 Johnson Dec. 30, 1947 2,434,253 Beck Jan. 13, 1948 2,435,988 Varian Feb. 17, 1948 2,455,224 Buchwalter et al. Nov. 30, 1948 FOREIGN PATENTS Number Country Date 883,665 France July 12, 1943 OTHER REFERENCES Ser. No. 353,755, Dallenbach (A. P. 0.), published May 25, 1943. 

